This invention relates to an electroluminescent (EL) panel and, in particular, to an EL panel from which smaller lamps can be made from a completed panel. As used herein, an EL “panel” is a single substrate including one or more luminous areas, wherein each luminous area is an EL “lamp.”
An electroluminescent (EL) lamp is essentially a capacitor having a dielectric layer between two conductive electrodes, one of which is transparent. The dielectric layer can include a phosphor powder or there can be a separate layer of phosphor powder adjacent the dielectric layer. The phosphor powder radiates light in the presence of a strong electric field, using very little current.
A modern (post-1985) EL panel includes a front electrode that is typically a thin, transparent layer of indium tin oxide or indium oxide on a substrate such as a sheet of polyester or polycarbonate, which provides mechanical support for the other layers. Such coated sheets are commercially available. The panel is typically made by screen printing a phosphor layer on the front electrode, then screen printing a dielectric layer on the phosphor layer, and then screen printing a rear electrode on the dielectric layer. Individual lamps are made by cutting or punching the sheet.
An EL lamp is luminous only where the front electrode and the rear electrode overlap and there is an AC voltage across the electrodes. It is relatively easy to make electrical contact to the rear electrode. The front electrode is buried between the transparent substrate and the phosphor layer. Typically, the screen printed layers are patterned or are printed over a slightly smaller area than the front electrode to expose a portion of the front electrode in a finished lamp. Simply cutting a lamp into two or more pieces does not necessarily make smaller lamps. One needs access to both electrodes.
U.S. Pat. No. 5,491,379 (Daigle et al.) describes an EL panel in which the front electrode is exposed along one edge of the panel and a conductive contact is printed on the exposed front electrode and over a portion of the rear electrode, separated from the rear electrode by an insulating layer. This provides electrical contact to both electrodes within a small area on the rear of the lamp. A plurality of such contacts are printed along the length of the panel, corresponding to the locations of the lamps. U.S. Pat. No. 3,109,959 (DeLaChapelle et al.) discloses essentially the same idea implemented in pre-1985 technology; i.e. the lamp layers are not screen printed and a metal clip (rather than a screen printed conductor) extends around the layers to make contact with the front electrode. The clip is separated from the rear electrode by an insulating layer.
U.S. Pat. No. 5,821,691 (Richie et al.) discloses an EL panel in which the contact for a front electrode extends continuously along a long edge on the back of the panel whereby the contact does not restrict or define the location of lamps in the EL panel, enabling a plurality of lamps of various sizes to be included in a single panel.
The prior art relates to providing for custom or individual lamps during manufacture; viz. by providing a connection to the front electrode. This is fine for a large number of lamps. Manufacturing a small number of lamps, e.g. one or two up to a few dozen, is expensive and usually not commercially viable. What is needed in the art is a method for making custom lamps from a finished, larger EL lamp and a kit for doing so. By “finished” is meant that the lamp or panel includes all necessary layers and is suitable for sale in markets other than the low volume, custom lamp market as a completed lamp or panel.
The ability to make smaller EL lamps from panels could be of interest both to the manufacturer of EL panels and to customers that buy a large amount of EL lamps but discover they have an excess supply. A small volume, custom lamp maker is a potential customer for lamps from either source.
Often the person making a custom EL lamp is primarily in another business; i.e. he is not one of ordinary skill in the art of making EL lamps and the lamp is but a component in a product. Thus, one has the problem of providing a method and apparatus that can be used by a relatively unskilled person, yet have a very high rate of success in making a commercially viable lamp.
In view of the foregoing, it is therefore an object of the invention to provide a method for economically making custom lamps from a finished large area lamp or panel.
Another object of the invention is to provide a kit for economically making custom lamps from a finished large area lamp or panel.
A further object of the invention is to provide a method for salvaging EL panels for other uses.
Another object of the invention is to provide reliable access to the front electrode in an EL panel cut from a larger panel.
A further object of the invention is to provide a method and apparatus that can be used successfully by those unskilled in the art of making EL lamps.